US1966332A - Method of making photographic images in dyed silver iodide - Google Patents

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July 10, 1934 J. G. cAPsTAl-'F ET A1. 1,966,332 METHOD 0F MAKING PHOTOGRAPHIC IMAGES IN DYED SILVER vIDIDE Filed June 2, 1932` Sh 8 SGMSJ@ u r 111/ rl Silver '7 l 5 amedfmgpomsmiqdfde. l

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Patented July 10, 1934. l n

METHOD F MAKING PHOTOGRAPHIC IMAGES IN DYED SILVER IODIDE John G. Capstal! and Merrill W. Seymour, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New York Application June2, 1932, Serial No. 615,032

7 Claims. (Cl. 95-6) This invention relates to a method of making ordinary sodium thiosulphate solution, or it may photographic images in silver iodide and parbe removed with an oxidizing bleaching solution, ticularly to a method of making color images. leaving only the negative silver iodide image.

It is well known that positive silver images The silver iodide image may be used to mordant may be made by uniformly exposing a silver various basic dyes andso yield colored images b bromide emulsion to light, converting the silver bathing in the dye solutions. bromide .to silver iodide by means of potassium Alternatively, basic dyes may be incorporated iodide solution, exposing the converted emulsion in the silver iodide emulsion at the time of maklo a, desired subject, and developing in a vigorous ing. This is done preferably by having the dye m photographic developer. It has also been found present at the time of precipitation of the silver that, by treating the silver iodide emulsion with iodide. A 'deeply dyed silver iodide is thus obpotassium bromide together with certain desensitained. The excess of soluble salts is washed tizing dyes, a reversed image may be obtained. from the emulsion in the usual manner. -The A brief explanation will make clearer the basis coated and'dried plates are then treated with of the process just described and that of our inthe chemical sensitizer as above, uniformly exvention. In order to form a developable latent lposed to strong light, washed to remove the image in a silver iodide and gelatin emulsion by chemical sensitizer, treated with a solution of the action of light, the presence of an iodine potassium iodide, dried, exposed to the desired acceptor at the time of exposure is necessary. subject and developedin apowerful photographic 2 Various substances may function in this role, developer.

among them being sodium sulte, sodium hy- The plate is then bleached in an oxidizing soludroxide, and monomethyl-paramido phenol. tion. At this stage it will be found that the If, on the other hand, no acceptor is present dye has been liberated in the places where the at the moment of exposure, but instead potassilver iodidel was reduced to silver and that a sium iodide is in contact with the silver iodide, negative dye image remains adsorbed to silver s not only canno developable negative image be iodide. formed but any latent image whichl may have Our invention makes use of the same principles been present will be bleached or reversed on furas first outlined, but has certain advantages over ther exposure to light. In the method above, the older method. We start with a silver iodide the latent image formed in silver bromide is emulsion and sensitize it or bath it in an iodine 35 not destroyed when the silver bromide is conacceptor. This renders the silver iodide suscepverted to silver iodide. After the conversion, tible to the formation of a latent image upon however, there is excess of potassium iodide presexposure to light. The plate is then uniformly ent and further exposure bleaches the already exposed or fogged. The sensitizer (iodine ac- 5 fogged silver salt and thus yields a positive image. ceptor) is next washed out, and the plate bathed 90 We have found that it is possible to start with in potassium iodide solution. The silver iodide a silver iodide emulsion and obtain either a posiis now in a state such that further exposure .tive silver image or a negative silver iodide image. bleaches the latent image already formed to an Our invention, briefly, is carried out as follows extent dependent upon the amount of such exreference being made to the accompanying drawposure, and thereby forms a positive image on ing, in which there is shown in the form of a flow exposure to a light image. The plate is desheet the relation of the several steps of the veloped in a powerful developer and may thereprocess: y after be treated in one of several ways.

A silver iodide emulsion is bathed in a chemi- One of the chief advantages in our invention cal sensitizer, such as a dilute solution of sodium lies in the fact that basic dyes may be readily sulphite or sodium hydroxide, dried, and uniincorporated in, or mordanted to, the silver iodide formly exposed to a strong light. After this exemulsion at the time of making and this dye reposure, the plate is thoroughly washed to remainsinthe emulsion throughout the subsequent move the chemical sensitizentreated with a soluoperations until the silver image is bleached.

0 tion of potassium iodide and dried. The plate This makes it possible to prepare several iodide 105 is now exposed to a light image and developedin emulsions dyed with different colors and to mix a powerful photographic developer. A positive these dyed emulsions, each kind of grain retainsilver image and a negative silver iodide image ing its specic color sensitivity. Such mixed are present at this point. emulsions may then be used for a direct color The positive silver image may be fixed by an processinwhich the grains of the different colors 110 are simultaneously exposed and treated by various chemical reagents.

It also makes it much more convenient to produce a monochrome image. If one starts with silver bromide, fogs, converts to silver iodide and then produces the reversal image, the plate must be dyed in the later stages by a separate operation. Our invention obviates this.

In a preferred form of our invention, we proceed as follows:

A silver iodide emulsion containing a dye is made. For this we may use, by way of example, the following formula:

Solution I Gelatin, 121/2% solution 30 cc. Silver nitrate, 100 grams per liter 15 cc. Basic dye, 1% solution 10 cc. Solution I I Gelatin, 12 l/2% solution 30 cc. Potassium iodide, 100 grams per liter 17 cc.

Solution II is poured into Solution I with vigorous stirring and is made into an emulsion by methods which are well known and which include setting, shredding, washing, remelting and coating.

A large number of dyes are available for use in making this emulsion, two examples being Malachite green and Pyronine G, these dyes having respectively the British Color Index numbers 657 and 739.

After plates or films coated with this emulsion are dried, they are bathed in a chemical sensitizer, such as for example a 1/% solution of sodium sulphite or a 116% solution of sodium hydroxide. The plates are then dried and uniformly exposed to a strong light. After exposure, the plates are thoroughly washed to remove the chemical sensitizer and are then treated preferably with a 1% solution of potassium iodide. The plates are again dried. They are next exposed to the desired subject. They are then developed in a powerful photographic developer, such as what is well known in the art as a caustic hydroquinone process developer. Finally, they are bleached in an oxidizing solution of which the following is a satisfactory formula:

Sulphuric acid, 100 grams per liter 4 cc. Potassium bichromate, 100 grams per liter 4 cc. Water to 200 cc.

It is found that the dye color-sensitizes the silver iodide, both for the first or fogging exposure and for the second or image-forming exposure. Thus, Malachite green makes the silver iodide red sensitive, while Pyronine G makes it green sensitive.

Our invention may be used advantageously to obtain monochrome dye images, since it requires less image-forming exposure than the process in which a negative silver image is developed from silver iodide and a positive dye image is subsequently obtained.

Our invention would likewise be useful in a. socalled mixed grain process, it being possible to mix intimately three separate portions of silver iodide emulsions, each dyed a different color, and then to process such a mixed emulsion bythe methods we have given.

It is understood that our invention is not limited by the examples given, but we contemplate as included therein all modifications and equivalents which fall within the scope of the appended claims.

What we claim is:

l. The method of producing photographic images which comprises precipitating a silver iodide emulsion, forming a layer therefrom, bathing with an iodine acceptor uniformly exposing the layer to light, treating the layer with an alkali iodide, exposing it to a light image and developing the image.

2. The method of producing photographic images which comprises chemically sensitizing a silver iodide emulsion layer, uniformly exposing.

said layer to strong light, removing any excess chemical sensitizer, treating the layer with a solution of potassium iodide, exposing the layer to alight image, and developing.

3. The method of producing photographic images which comprises chemically sensitizing a silver iodide emulsion layer, uniformly exposing said layer to a strong light, washing the layer to remove the chemical sensitizer, treating the layer with a solution of potassium iodide, exposing the layer to a light image, and developing in a powerful photographic developer.

4. The method of producing photographic images which comprises precipitating an emulsion containing silver iodide and dye absorbed to the silver iodide, forming a layer therefrom, uniformly exposing the layer to light, treating the layer with an alkali iodide, exposing it to a. light image, developing a silver image in the layer and removing the silver image and the dye associated therewith, thus leaving a dyed silver iodide image.

5. 'I'he method of producing a photographic color image which comprises chemically sensitizing a silver iodide emulsion layer, uniformly exposing said layer to a strong light, washing the layer to remove the chemical sensitizer, treating the layer with a solution of potassium iodide, exposing the layer to a light image, developing in a powerful photographic developer, removing the positive silver image with an oxidizing bleaching solution, and mordanting a dye to the remaining silver iodide image.

6. The method of producing a photographic color image which comprises chemically sensitizing a silver iodide emulsion layer, uniformly exposing said layer to a strong light, washing the layer to remove the chemical sensitizer, treating the layer with a solution of potassium iodide, exposing the layer to a light image, developing in a powerful photographic developer, removing the positive silver image with an oxidizing bleaching solution, and mordanting a basic dye to the remaining silver iodide image.

7. The method of producing a photographic color image which comprises chemically sensitizing a silver iodide emulsion layer containing a basic dye absorbed to the silver iodide, uniformly exposing said layer to a strong light, washing the layer tov remove the chemical sensitizer, treating the layer with a solution of potassium iodide, exposing the layer to a light image, developing and then removing the devloped image, leaving a dyed silver iodide image.

JOHN G. CAPSTAFF. MERRILL W. SEYMOUR.

Patent No. 1,966,332.

CERTIFICATE 0F o0RRECT10iJ.` y

July i0, 1934.

JOHN G. CAPSTAFF, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, lines 105 and 138, claims 4 and 7, respectively. for "absorbed" read adsorbed; and that the said Letters Pater.: should be read with these corrections therein that lthe same may conform to the record ef the case in the Patent Office.

Signed and sealed this 11th day ofA September, A. D. 1934.

Leslie Frazer (Seal) l' I Acting Commissioner of Patents.

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